Binaural magnetic recorder



July 24, 1951 M. cAMRAs BINAURAL MAGNETIC RECORDER 2 SheetS-Shee?l l Filed Dec. 3l. 1946 3v. bv N Patented July 24, 1951 BINAURALMAGNETIC RECORDER Marvin Camras, Chicago, Ill., assignor to Armour Research Foundation of Illinois Institute of Technology, Chicago, Ill., a corporationof Illinois Application December 31,r l1946, Serial No. 719,385

7 Claims. (Cl. FX9-100.2)

This invention relates to magnetic recording and reproducing devices, and more particularly, to a binaural magnetic recorder and reproducer.

Binaural effects with magnetic recording and reproducing apparatus have been suggested in the past, such as the one described in the A. L. Curtis Patent No. 1,591,081, granted July 6, 1926.

The fundamental concept of a binaural system is to have a plurality of sound tracks which are recorded simultaneously through separate pickup devices located at different points in space, and then playing back the recorded sound tracks with sound reproducing elements located at different points in space.

One of the principal features and objects of the present invention is to provide an improved binaural recording and reproducing means.

A further object of the present invention is to' provide a binaural system in which the sound tracks are carried on a tape carrier, and in which half of the sound tracks are used by moving the tape in one direction and half of the sound tracks are used by moving the tape in the other direction.

Another object of the present invention is to provide novel head means for binaural recording and reproducing apparatus.

Afstill further object of the present invention isl to provide a novel arrangement and structure of erasing means and magnetic recording and reproducing means.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization, manner of construction, and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in which: y

Figure 1 is a block diagram of a binaural magnetic recording system embodying the novel teachings and characteristics of the present invention;

Figure 2 is a diagrammatic sketch of a fourlane tape used in connection with the system illustrated in Figure 1;

Figure 3 is an isometric view showing a magnetic head assembly for the binaural magnetic recording system of Figure 1;

Figure 4 is a vertical sectional view taken along the line IV-IV of Figure 3;

Figure 5A is a front elevational view of one of the recording and reproducing heads of the head assembly shown in Figure 3;

Figure 6 is a diagrammatic illustration of a modified form of tape wherein more than four y ductors I6 and I1 to two high frequency ampli.

fiersv I8 and I9, where the audio component is mixed with the high frequency component and then fed through conductors 20 and 2I, respectively, and through equalizers 22 and '23 to electromagnetic transducer heads 24 and 25.

Suitable switches 26 and 21 are interposed in the circuit between the equalizers 22-and 23 and the electromagnetic transducer heads 24 and 25 for a reason which will presently be apparent,

A `high frequency oscillator 28 is provided for supplying the highfrequency component to the high frequency amplifiers I8 and I9, and this high frequencyv signal may vary in frequency throughout a wide range without departing from the spirit and scope of the present invention. By

way of illustration, and not by way of limitation,

this high frequency component may be in the order of 40 kilocycles.

The high frequency `oscillator 28 also feeds i into an erase amplifier 29, which, in turn, connects with the erase' head 30 of the magnetic head assembly 3 I.

heads 24 and 25, as well as the erase head 30.

`The recording is arranged to be made on a tape 32 (see Figure 2) lwhich includes four sound tracks 33, 34, 35 and 36. These sound tracks are arranged to be used in pairs. As illustrated in Figures 1 and 2, the sound tracks 33 and 34 are arranged to be simultaneously recorded on when the tape is moved from left to right, while the tracks 35 and 36 are arranged to be recorded on when the ends of the tape have their positions reversed and the tape is then moved from right to left. This will be apparent from an inspection of the diagrammatic representation of the head assembly 3l., Y

V In addition to the heads 24, 25 and 30 in the head assembly. 3|, there is also provided three keepers 31, 38 and 39, which are formed of a high permeability, low coerciveforce material. The

This magnetic headl assembly 3I includes the two electromagnetic transducer' keeper 31 lies adjacent the head 24 and extends from a position near the erase head to a position near the transducer head 25. The keeper 38 lies opposite the transducer head 25 and extends from the transducer head 24 to a position beyond the location of the head 25. Thekeeper 39is of a width slightly greater than the two tracks 35 and 36 on the tape 32 and lies opposite the erase headVA 30, the transducer head 24, and the keeper 38. As

will presently be explained, the use'of these keep*- ers in this head assembly tends to eliminate crossy talk and unwanted pick-up or play back between adjacent channels on the tape 32.

For reproducing purposes, the switches I2, I3, 26 and 21 are thrown from their full line positions to their dotted line positionsyand this connects the transducer heads 24 and 25 to the input side of the audio ampliers I4 and I5 through oonductors 40 and 4 I respectively. Y

The outputs oftheaudio"a'mplilersV I4 and I5 are connectedvv through Vconductors 42 and 43 to the two sound` reproducing means 443-andif45 re-f f spectively. These sound reproducing :means m'a-y be the two phone units of a head-phone set,` or they may be two loudspeakers located inl spaced relationship so' as to be located at the same two relative positions as the microphones IU' and II, when the recording was made. `The desired bi-l naural Veffect will thereby be produced.l

The structural arrangement ofthe magnetic two U-shaped members 46'and 41 in snug nested engagement therewith. The L-shaped members 48' and 43 have' their short legs projecting toward l each other to form polesr with'a 'non-magneticigap` EUlying therebetween.

The tape 32 is arranged toY ride over thevpoleportions of the core members'48 and' 49" and' across Vth'egap 50.

,Asi-nai @011 5| is' mounted on one of the legsV of the core structure` in the manner illustrated. The' erase head 30' is similar t'd'they electromagnetic transducer heads 24 and 25 with the exception that the non-magnetic gap`52 is dispos'ed'at an acute angle with respect to the lengthwise, Y

movement of the 'tapez 32. This' may be' seen clearly in Figures 11and3 of the drawings, where' the non-magnetic gap 52 lies at 'an acute angle', while the gap of the heads 24 and 25 is exactly at right angles to the direction of travel of the" tape. This places the rerase vgap vat an angle with` respect to the gaps of the recordinghe'ads.

As may be seen best in Figures 3 andl of the drawings, the two electromagnetic transducer'.

heads 24 and 25 and the erase head Stare assembled in a two-piece housing of 'non-magnetic', non-conducting material, such, for example, .as Bakelite, indicated generally at 53. This hou`s.

ing includes a rear housing member 54andA a front housing member 55 which are' provided with confronting recessed portions in'tol which the heads 24, 25 and 3'are assembled. The upper wall of the front housing member 55 is ,provided with suitable openings through .whichrthe pole portion of each ofthe heads 24', A25'and 3'project Very slightly.

Also mcrmtecly in the upperwallportion o'fthe 4 front housing member 55 are the two keepers 31 and 38. It will be noted that keeper 31 is arranged to lie against track 33, while keeper 38 is arranged to lie against track 34 when the tape is being moved from leftto right as viewed in Figure 1 of` the'drawings'. y

In addition tothe keepers 31 and3, the keeper 39 is carried in the rear housing member 54 and lies against the tracks 35 and 36 of the tape 32, when'` the tape is being moved from left to right as Viewed in Figure l of the drawings. It will be noted from an inspection of the drawings that the keepers 38 and- 39 prevent the magnetic eld set upA by the head' 24 during the recording process from influencing the adjacent channels on the tape 32,'and ontplay-back prevents stray pick-up from the adjacent channels by head 24. e Keepers 31 and 39 prevent the magnetic eld set up by the head 25 during `the recording process fromy influencing the adjacent channels on` the u tape Y32, and on play-back prevents 'stray pick-upf from' the` adj acent' channels" being'V pickediup' by head 25. y The staggered arrangement of"thel'leads 24:1 and 25 in conjunction with theikeepers 3,1Y and 38' also tends to greatly improve'the simultaneouskv operation of the two heads, as; is necessary in a binaural system. 4 y f In Figure 6 of the drawings, I'have .illustratedthe tape with six ch'annels';66^,161,.6`8, .691.1U`and1l2` l thereon, three of which will'. 'be recorded on orM4 played' back from when thel tape'is 'moved one direction, and the other vthree'ofl which are used" when the tape is reversedv end' to endv and"moved. back in the opposite direction. Y

With such an arrangement, three sets' ofjheads will, of course, be employed, anda keeper13will p be employed having a portion .associated"witfh each head as is illustratedin Figure'lf thedraw; 1 ings. More particularly, as. shown in( Figure .7kv ofV the drawings, the head assembly Bfor a'six-'l'ane tape would employ Aan erasehead 51 `which is substantially half` of the widthf of the tape .and three electromagnetic.transducer heads 58 59and. t5', which are each slightly. less thana .sixth of` the width of the tape-I Afsingle magnetic keeper 13 is employed having. integral .portions 6I, 2',- 63', 64 and 55. The portions 6I' and. 64- extendinf a lengthwise direction away from,the..head 5S,l-.} while the portions 62- and-.6.3. extend lengthwise away from the heads .G''andf58frespectively# The portion 55 'is sul'ostantially half.` of ,the wid-thu-off. l' the tapeand extends vacross Vthe whole head- ;as=

' sembly as showninFigure?. p

It will bje .observed battue-neas sa.1iesiuA f` openingl 12 in the Akeeper.` 13,.` andv thus .thehead, 53 is completelysurroundedbya magnetic keeperr AThis is aA particularly effective typev ofshielding.

and may be employed with one or more head-s;A l

With .an arrangement suchas `illustrated'. comecuonrwitnr'igures 6V ,andrei me drawings, it will', of course, be understood;that.eachof the.4 f electromagneticVv transducer headsES", '59 an'dllf. will have a microphone and a ySound reproducing: means associated therewith, such as Vthe 'microf A phone I0 and the sound reproducing means 44 01....' Figure l. L In the foregoing specification .and thel accom? panying claims, I haveusedthe Aterm' paramagf netic to designate a materialh'aving a' high value oi'magneticI permeability as compared toair'su'cl. as, for example, soft iron@v Y While I haveshjown 'certain particular.embodn-- l.

stood that I do notwisntc'be'umitedthret, "i

graces@ Since many modications may be made,fand"'-I,'

therefore,- contemplate by the appended claims to cover all such modifications as'wall within the true spirit'and scope of my invention.

I claim as my invention: v

1. An electromagnetic transducer head assembly comprising a magnetic record member supporting means along which a record member is arranged to travel, a pair of Aelectromagnetic transducer heads mounted in said assembly and spaced both laterally and longitudinally with respect to each other, a paramagnetic member alongside each of said heads and. longitudinally aligned with the lother of said heads, whereby each of said heads is associated with a dierent longitudinal region of said record member, and whereby each of said heads is substantially isolated to its associated longitudinal region of said record member.

2. An electromagnetic transducer head assembly comprising a magnetic record member guiding and supporting means including a supporting surface along which a record member is arranged to travel, a pair of electromagnetic transducer heads mounted in said assembly and spaced both laterally and longitudinally with respect to each other, said heads each including a pair of polar portions separated from each other by a non-magnetic gap, said polar portions having a supporting surface forming at least part f the Supporting surface of said supporting means, a paramagnetic member alongside each of said heads and forming a part of said supporting surface of said supporting means and longitudinally aligned with the other of said heads, whereby each of said heads is associated with a different longitudinal region of said record member and whereby each of said heads is substantially isolated to its associated longitudinal region of said record member.

3. An electromagnetic transducer head assembly comprising a magnetic record member supporting means along which a record member is arranged to travel, a pair of electromagnetic transducer heads mounted in said assembly and spaced both laterally and longitudinally with respect to each other, a paramagnetic member alongside each of said heads and longitudinally aligned with the other of said heads, whereby each of said heads is associated with a different longitudinal region of said record member, and whereby each of said heads is substantially isolated to its associated longitudinal region of said record member, said heads and said paramagnetic members being dimensioned and positioned so as to cover substantially one-half of the width of the record member which the head assembly is arranged to receive.

4. An electromagnetic transducer head assembly comprising a magnetic record member supporting means along which a record member is arranged to travel, a pair of electromagnetic transducer heads mounted in said assembly and spaced both laterally and longitudinally with respect to each other, a paramagnetic member alongside each of said heads and longitudinally aligned with the other of said heads, whereby each of said heads is associated with a diierent longitudinal region of said record member, and whereby each of said heads is substantially isolated to its associated longitudinal region of said record membensaid heads and said paramagnetic members being dimensioned and positioned so as to cover substantially one-half of the width of the record member which the head assembly is member lying alongside of said head and said paramagnetic member which lie closest to the center line of travel of said record member, said third paramagnetic -member underlying substantially fthe other half of the width of said record member. y

5. Anelectromagnetic transducer head assembly comprising a magnetic record member supporting means valong which a record member is rarranged Ato travel, a pair of electromagnetic transducer heads mounted in said assembly and spaced both laterally and longitudinally with respect to each other, a paramagneticv member alongside each of said heads and longitudinally aligned with the other of said heads, whereby each of said heads is associated with a different longitudinal region of said record member, and

whereby each of said heads is substantially iso-V lated to its associated longitudinal region of said record member, said heads and said paramagnetic members being dimensioned and positioned so as to cover substantially one-half of the width of the record member which the head assembly is arranged to receive, and an erase head lying opposite the end of one of said paramagnetic members and the head which lies alongside said last mentioned paramagnetic member, said erase head covering substantially one-half of the width of the record member which the head assembly is arranged to receive.

6. An electromagnetic transducer head assembly comprising a magnetic record member supporting means along which a record member is arranged to travel, a pair of electromagnetic transducer heads mounted in said assembly and spaced both laterally and longitudinally with respect to each other, a paramagnetic member alongside each of said heads and longitudinally aligned with the other of said heads, whereby each of said heads is associated with a different longitudinal region of said record member, and whereby each of said heads is substantially isolated to its associated longitudinal region of said record member, said heads and said paramagnetic members being dimensioned and positioned so as to cover substantially one-half of the width of the record member which the head assembly is arranged to receive, and an erase head lying opposite the end of one of said paramagnetic members and the head which lies alongside said last mentioned paramagnetic member, said erase head covering substantially one-half of the widthof the record member which the headassembly is arranged to receive, and a third paramagnetic member lying alongside of Said erase head as well as the one of said transducer heads and paramagnetic member which lie closest to the center line of the path of travel of said record member, said third paramagnetic member underlying substantially the other half of the width of said record member.

7. An electromagnetic transducer head for operation in conjunction with a magnetic record medium capable of accommodating a plurality of spaced tracks, said head including a pair of paramagnetic core members each defining a nonmagnetic gap and having portions adjacent thereto to receive said medium, said portions of one of said core members extending over substantially the width of one of said tracks and said portions of the other of said core members extending over substantially the width of the other of said tracks, and a pair of paramagnetic keeper members in engagement with said medium, one

arranged to receive, and a third paramagnetic of said members being in longitudinal alignment 1,' with.. said:A first, :core .member and: extending; over Number E said; other,dirimirr andthe other of sa-dfkeeper. 23089287 members being in `longitudinal alignment with 2,144,844 said .other -eorev member` andextending over saidv 2,167,188 oxrieftracl,A said kerepersezlabeing Vspexzed-12ter 5 2,229,326 ally of the associated core member. Y 1 2,335,277 y MARVINCAMRAS. 2,361,752v

REFERENCES.- CITED/ n The' following references are of recordA inthe 10 Number file of this' patent: .19,133 .Y UNITED STATES PATENTS Number Name Date 58342881 1,971,028

Bothe Aug. 21, 1934 15 Name Date Malloy .Aug. 10, 1937 Hickman Jan. 24, 1939A 1 Schaar-achter July 25, 1939 Heller ,J an. 21,l 1941 Heller'm Nov..30, 19.43 Eilenberger Oct. 31,1944.

FOREIGN. .PATENTS Country Date Australia Jan.. 28, 1930V lE Treagt Britain Aug. .2, 1929,v Germany Jan. 18,1941. 'France Aug! .30;V V19413 

